Question

What would be the best (fastest) way to parse through a mmap-ed file? It contains pairs of data (string int), but I cannot persume number of whitespaces/tabs/newlines between them.

Answer 1

Assuming you’ve mmaped the whole file in (rather than chunks – as that would make life awefully complicated), I’d do something like the following…

// Effectively this wraps the mmaped block
std::istringstream str;
str.rdbuf()->pubsetbuf(<pointer to start of mmaped block>, <size of mmaped block>);

std::string sv;
std::string iv;

while(str >> sv >> iv)
{
  // do stuff...
}

I think that should work…

WARNING This is implementation defined behaviour, see this answer for an altogether better approach.